This application represents an effort towards studying several aspects of T cell biology, via investigations of the T receptors. In some experiments proposed, particular antigenic properties of some T cell receptors constitute the primary object of study; in others, a specific pattern of receptor expression (which emerges under defined conditions of T cell selection, in vitro) is the starting point for further functional and structural experimentation. Long term development of such experiments might contribute to the understanding of the complex cellular interactions which lead to the selection of a functional T cell repertoire. Our main objectives are: - to analyze the structural basis of antigenic similarity between MHC class II epitopes and some T cell receptor alpha/beta idiotypes (as expressed by two T cell hybrids). - to investigate the effects of T gamma-allotypic suppression on various immune functions. - to investigate comparatively gamma/delta heterodimers expressed by MLR-selected "double negative" T cells and by a subset of thymocytes. - to investigate the potential TcR (alpha/beta) repertoire of nude mice, and revealed in an in vitro system of mass differentiation, in the absence of any thymic elements. To achieve our goals, we will perform a variety of in vitro and in vivo experiments, using cellular immunology techniques as well As some molecular biology and protein chemistry procedures. A special attention will be given to the production of anti-T gamma-allotype monoclonal antibodies, the BALB/c versus DBA/e combinations.